Continuous steam-iron process

ABSTRACT

In a continuous steam-iron process wherein finely divided iron oxides are reduced in a reduction zone and the reduced iron oxides are reacted with steam in an oxidation zone to make hydrogen, the reduction of the iron oxides is effected by means of a continuously recirculating stream of hot, finely divided carbonaceous solids which are mixed with the iron oxides in a downwardly moving bed under reducing conditions, and heat is supplied to the reduction zone by the carbonaceous solids which are heated by partial combustion outside the reduction zone. In the preferred embodiment of the process, the mixture of reduced iron oxides and carbonaceous solids from the reduction zone is separated in a fluidized separation zone into a stream of reduced iron oxides and a stream of carbonaceous solids. The stream of reduced iron oxides is conducted to the oxidation zone where the reduced iron oxides fall through a fluidized bed of hydrocarbonaceous solids in countercurrent flow relationship to steam, whereby a product gas is produced which contains methane by virtue of the reaction of the hydrogen (produced by the steamiron reaction) with the hydrocarbonaceous solids.

United States Patent [72] inventors James L. Johnson Oak Park; Frank C.Schora, Palatine; Paul B. Tarman, Elmhurst, all of III. [211 App]. No.798.334 [22] Filed Feb. 11, 1969 I45] Patented Nov. 9, 1971 [73]Assignee Consolidation Coal Company Pittsburgh, Pa.

[54] CONTINUOUS STEAM-IRON PROCESS 8 Claims, 5 Drawing Figs.

[52] 0.8. CI 23/214, 23/200, 23/212. 23/284, 48/197 [51] lnt.Cl C0lbl/07, I C0lb 1/02 [50] Field oi Search 23/214, 2 12, 210, 200

[ 56] References Cited UNITED STATES PATENTS 2,449,635 9/1948 Barr23/214 2,602,809 7/1952 Dickinson 23/214 X 2,640,034 5/1953 Jones 23/214X 3,017,250 1/1962 Watkins 23/214 Primary Examiner-- Edward SternAlwmeys- D. Leigh Fowler, Jr. and Stanley J. Price, Jr.

ABSTRACT: In a continuous steam-iron process wherein finely divided ironoxides are reduced in a reduction zone and the reduced iron oxides arereacted with steam in an oxidation zone to make hydrogen, the reductionof the iron oxides is e1- fected by means ofa continuously recirculatingstream of hot, finely divided carbonaceous solids which are mixed withthe iron oxides in a downwardly moving bed under reducing conditions,and heat is supplied to the reduction zone by the carbonaceous solidswhich are heated by partial combustion outside the reduction zone. Inthe preferred embodiment of the process, the mixture of reduced ironoxides and carbonaceous solids from the reduction zonev is separated ina fluidized separation zone into a stream of reduced iron oxides and astream of carbonaceous solids. The stream of reduced iron oxides isconducted to the oxidation zone where the reduced iron oxides fallthrough a fluidized bed of hydrocarbonaccous solids in countercurrentflow relationship to steam, whereby a product gas is produced whichcontains methane by virtue of the reaction of the hydrogen (produced bythe steam-iron reaction) with the hydrocarbonaceous solids.

EFFLIENT GAS 5- ASH LIFT PIPE PATENTEDunv 9 Ian 3,6 1 9, 142

sum 1 or 5 EFFLUENT GAS 8: ASH

' REACTOR EFFLUENT REDUCTION ZONE LIFT PIPE PRODUCT c5 R Ep 5 s ous GASsouos O M O U OXIDATION zone CARBONACEOUS l8 STEAM FIG 1 nvvsnrons.

JAMES L. JOHNSON FRANK C. SCHORA, JR,

PAUL B. TARMAN PAIENTEnuuv 9 I9?! CHAR SHEET 2 0F 5 REDUCTOR EFFLUENT"ieaa i FIG. 2

AIR FLUIDIZING GAS PRODUCT eAs STEA M FRANK C. SCHORA, JR.

PAUL B. TARMAN PATENTEDunv 9 Ian SHEET 3 BF 5 PRODUCT GA$ REDUCTOREFFLUENT REDUCTOR INVENTORS. JAMES L. JOHNSON FRANK C.SCHORA,JR. PAUL B.TARMAN STEAM CONTINUOUS STEAM-IRON PROCESS This invention relates to animprovement in the steam-iron process for making hydrogen or fuel gas.

The steam-iron process is a process for making hydrogen by the reactionof steam with either elemental iron or a lower iron oxide, for example,FeO. The reaction produces higher oxides of iron, for example, Fe Owhich may be reduced to repeat the cycle.

Despite the apparent simplicity of the steam-iron process and despitethe fact that it has been known and worked on for over 100 years, to thebest of our knowledge no technically and economically feasibleembodiment of a continuous steamiron process has been developed which isnow practiced commercially. Perhaps the principal reason for the failureof the steam-iron process to achieve commercial success is thedifficulty involved in making it a continuous process. To do so requiressubjecting a continuously flowing recirculatory stream of iron oxides totwo different reactions, namely oxidation and reduction, under optimumconditions for each reaction, including optimum input and distributionof the heat required in the process.

Prior continuous steam-iron processes have favored the use of gaseousreductants for reducing the iron oxides (see, by way of illustration,U.S. Pat. No. 2,198,560). However, the production of a suitable gaseousreductant is expensive, and renders the overall process uneconomical.Furthermore, because of the limitations imposed by the thermodynamicequilibrium during the reduction of Fe O and FeO to FeO and Fe withreducing gases containing hydrogen and carbon monoxide, the off-gas fromonce-through reduction contains considerable unreacted hydrogen andcarbon monoxide. Thus, such a process tends to be wasteful of reducinggas.

In the copending application of Homer E. Benson, Ser. No. 598,072, filedNov. 30, 1966 and assigned to the assignee of the present invention, thereducing gas is made in silu by reacting air and carbonaceous solids inthe presence of the iron oxides. Such a process has many advantages butrequires careful control to minimize reconversion of elemental iron tohigher oxides by contact with air.

Continuous steam-iron processes have been proposed which utilize eithera solids in gas dispersion or the fluidized solids technique in theoxidation zone and the reduction zone (see, by way of illustration, U.S.Pat. Nos. 2,602,809 and 3,017,250). Reducing systems employing adispersion of powdered iron oxide in a suspending gas call for largereactors and costly gas-solids separators. All attempts to operate withthe iron oxide in a fluidized condition have failed to becomesufficiently attractive for commercial adoption because a fluidized massis of uniform composition throughout whereas a composition gradient isgenerally desired.

In accordance with the present invention we have provided an improvedcontinuous steam-iron process which uses not only a recirculatory streamof particulate iron oxides, but also uses a recirculatory stream ofparticulate carbonaceous solids to effect reduction of the iron oxidesand to supply process heat requirements. In the practice of the processof this invention, reduced iron oxides comprising principally FeO and Feare oxidized by steam in an oxidation zone, and iron oxides comprisingprincipally Fe O and FeO are reduced in a reduction zone. By principallywe mean that at least 50 percent by weight of any mixture of oxidizableor reducible iron compounds, as the case may be, consists of theindicated compounds, and the actual percentage approaches I percentunder equilibrium conditions. The relative amounts of FeO and Fe in theoxidizable mixture, and the relative amounts of mo, and FeO in thereducible mixture are functions largely of the temperature, pressure,and residence time maintained in the respective reaction zones. Theoxidation of FeO and Fe (sometimes simply referred to herein as reducediron oxides) is accomplished by passing steam in reactive relationshipwith the reduced iron oxides in an oxidation zone. The reduction of Feo, and FeO is accomplished by subjecting them to direct contact with therecirculatory stream of hot carbonaceous solids in a downwardly movingbed in the reduction zone. No oxygen-(molecular) containing gases areintroduced into the moving bed in the reduction zone. The reductionconditions are selected to insure that only partial carbon depletion iseffected during the passage of the carbonaceous solids through thereduction zone, while however, the desired reduction of the iron oxidesto Fe and FeO is effected. Heat is supplied to meet the requirements ofthe process by partial combustion of the carbonaceous solids in acombustion zone located outside the reduction zone. The amount ofpartial burning is controlled to raise the temperature of thecarbonaceous solids sufficiently high to supply adiabatically the heatrequired.

In the preferred embodiment of the process, a separation zone isinterposed between the reduction zone and the oxidation zone to effectseparation of the carbonaceous solids from the reduced iron oxidesleaving the reduction zone. Separation is effected by passing a gasthrough the mixture of carbonaceous solids and reduced iron oxides at avelocity which pennits ready separation by virtue of the difference indensities of the iron compounds and carbonaceous solids. A fluidizedseparation zone is especially preferred wherein the fluidized bedconsists essentially of the lighter carbonaceous solids from which theheavier iron compounds may be withdrawn and sent to the oxidation zone.The oxidation zone in the preferred embodiment comprises a fluidized bedof fresh carbonaceous solids into which the reduced iron oxides are fed.Hydrogen is produced by the relatively fast reaction of steam andreduced iron oxides, and in turn reacts with the carbonaceous solids toform methane. The separated carbonaceous solids from the separation zoneare recirculated through the combustion zone back to the reduction zone.

The process operates continuously and efficiently to yield hydrogen or amethane-rich gas. The improvement in economics of the process ascompared with prior steam-iron processes is due to the efficient use oflow cost, finely divided carbonaceous solids for l the reduction of ironoxides, 2 the supply of process heat, and 3 in the preferred embodiment,the production of methane in a relatively simple two-vessel system. Thegain in efficiency in the reduction zone arises from the thermalgradient established in the downwardly moving bed and from the lack ofback-mixing of reduced iron. Thus, maximum reaction rates result fromthe countercurrent flow relationship of the upwardly flowing reducinggases (generated in situ) and the downwardly flowing fresh iron oxides.The absence of molecular oxygen-containing gases assures no loss ofdesired reduction as a result of competing reactions. The flow of gasesand solids in the oxidizer is most efficiently conducted in a fluidizedbed for the particular reactions involved, to thereby minimizetemperature gradients and to provide for an efficient balance betweenexothermic and endothermic reactions. Thus, in summary, the improvedprocess provides for the maintenance of the optimum conditions for thereduction of mo, to FeO to Fe, and for the oxidation of the reduced ironoxides with steam.

For a better understanding of our invention, its objects and advantages,reference should be had to the following description and accompanyingdrawings in which FIG. I is a diagrammatic drawing of our invention inits broadest aspects,

FIG. 2 is a diagrammatic drawing of the preferred embodiment of ourinvention,

FIG. 3 is the same diagrammatic drawing of FIG. 2 but showing thelocations of differentpoints in the solids and gas streams to aid inunderstanding the material balance run re ported in Table l of thespecification,

FIG. 4 is a schematic drawing of a modification of the preferredembodiment of FIG. 2; and

FIG. 5 is the same schematic drawing of FIG. 4 but showing the locationsof different points in the solids and gas streams to aid inunderstanding the material balance run reported in Table II of thespecification.

Referring to FIG. 1 of the drawings, the numeral 10 designates asuitable vessel for housing a reduction zone 12 and an oxidation zone14. The reduction zone consists essentially of a downwardly moving bedof solids which flows by gravity through an opening 16 into theoxidation zone. The downwardly moving bed of solids in the reductionzone consists essentially of a mixture of two recirculatory streams ofsolids moving in substantially concurrent flow relationship. The firststream of solids contains iron oxides which are principally Fe O andFeO. The second stream of solids contains carbonaceous solids whichserve not only to effect reduction of the iron oxides, but also toprovide adiabatically the heat required for the reduction reaction. Theprimary reactions which occur in the reduction zone are as follows:

2. C+FeO2Fel-CO 3. CO,+C 1 2 C0 The temperature maintained in thereduction zone is between l000 and 2600 F. The pressure may beatmospheric or superatmospheric. The size consist of the iron oxides maysuitably be in the range of 325 to 2 Tyler Standard screen. The sizeconsist of the carbonaceous solids may also suitably by in the range of325 to 2 Tyler Standard screen. The residence time of both solids in thereduction zone is generally between 15 seconds and 60 minutes.

The carbonaceous solids in the reduction zone may conveniently be asolid carbonaceous fuel that is noncaking under the conditions of thereduction zone. Suitable solids of this kind are noncaking coals,lignite, coke, char which is the solid product obtained by the pyrolysisof coal or lignite, or coals rendered noncaking by preoxidation. Suchsolids are generally ash-containing, and as will be shown later,provision must be made for discharging ash from the overall system toprevent its buildup beyond a given point. Actually, up to a point, theash serves as a heat carrier for maintaining the desired temperature inthe reduction zone. In general, the carbon content of the carbonaceoussolids in the reduction zone is at least 20 percent by weight. Theweight ratio of carbon to iron oxide in the reduction zone must besufficient to assure the required conversion of Fe O. and FeO to FeO andFe during the passage through the reduction zone. in the broadest aspectof this invention, the reduced iron oxides, together with carbondepletedcarbonaceous solids, flow into the oxidation zone without any attempt toseparate the two solids systems. This is not the preferred procedure aswill be seen in the description of the preferred embodiment. However, inthe case of very reactive carbonaceous solids, such as some lignites, itis feasible for them even in a carbon-depleted state to react with steamin the oxidation zone, even in the presence of iron or FeO. The lessreactive carbonaceous solids in a carbondepleted state would generallyconstitute a mass of relatively inert solids, 'thus reducing theeffective throughput in the oxidation zone.

In the oxidation zone, steam is introduced through a steam inlet 18 andis circulated in reactive relationship to the reduced iron oxides. Thereaction of steam with Fe and with FeO is extremely rapid andexothermic. The reactions are as follows:

5. H O+3Fe0;- F e O,+H Any gas-solids system may be used in theoxidation zone to make hydrogen because of the high rate of reaction ofsteam and the reduced iron oxides. If a fuel gas is the desired product,then the best system is determined by the reactivity of the carbonaceoussolids fed to the oxidation zone or by the extent of carbon gasificationdesired. For example, a free-fall system in which solids have arelatively short residence time may be used for highly reactivecarbonaceous solids, or in those instances where a relatively smallamount of carbon gasification is desired for less reactive carbonaceoussolids. Where significant carbon gasification is desired with lessreactive carbonaceous solids, a fluidized bed system may be used. Thetemperature maintained in the oxidation zone is generally between l000and 2000 F. The pressure may be atmospheric or superatmospheric. Theresidence time of the solids in the oxidation zone may be between 30seconds and 200 minutes. The higher pressures and longer residence timesfavor methane production andthe shorter residence times are suffrcientfor hydrogen production.

In addition to the reaction of steam with the reduced iron oxides tomake hydrogen, there will be some reaction of steam with anycarbonaceous solids that are present to produce CO and H as well as someCO- More importantly, the hydrogen produced by the steam-Fe, steam-FeO,or steam-carbon reaction will react with the carbonaceous solids toproduce methane, particularly at elevated pressures. If desired, freshcarbonaceous solids may be introduced into the oxidation zone through aconduit 22 to increase the content of methane in the product gas. Themixture of gases is discharged as product gas through a conduit 20 fordirect use or for further treatment or purification, as may be desired.

The solid product of the oxidation zone, principally FeO and Fe O alongwith unreacted carbonaceous solids, are withdrawn from the oxidationzone through a pipe 24 to a lift pipe 26 for recirculation to thereduction zone. The lift pipe 26 constitutes an elongated combustionzone for partially burning the carbonaceous solids with air introducedthrough an air feed pipe 28. Additional fresh carbonaceous solids mayalso be introduced through a feed pipe 30 to replenish the carbonconsumed in the oxidation and reduction zones, as well as in thecombustion lift pipe 26. The conditions maintained in the combustionlift pipe are such as to insure partial combustion of the carbonaceoussolids to raise the temperature of the upwardly flowing mass of solidsto a temperature sufficiently high to provide the necessary heat for thereduction reaction. As the carbonaceous solids recirculate through therecirculatory system, there is a buildup of ash. This ash may beseparated from the main stream of recircula'tory solids from the liftpipe 26 in a cyclone separator 32 or by other suitable means. The fluegas, plus such ash, is discharged through a pipe-34 while the mixture ofhot iron oxides and carbonaceous solids drops through pipe 36 onto thedownwardly moving bed in the reduction zone. The effluent gas from thelatter is withdrawn separately through a pipe 38.

The preferred embodiment shown diagrammatically in FIG. 2 is adapted toproduce a methane-containing gas that may be converted by conventionalmeans to a high B.t.u. gas. Fresh hydrocarbonaceous solids containingboth fixed carbon and volatile carbon are continuously fed to theoxidation zone, labeled Oxidizer in the drawing and also designated bythe numeral 42. The oxidation zone is contained in the lower part of avessel 40, the upper part of which confines the reduction zone 44,sometimes called Reductor. The fresh, hydrocarbonaceous solids bed tothe Oxidizer are high in total carbon content, in the range of 50 topercent by weight. Preferably we use either char, the noncaking solidproduct resulting from pyrolysis of coal or lignite at low temperature,or a raw coal which has been rendered noncaking, if necessary, bypreoxidation. The char, or raw coal (and hereafter reference is madeonly to char for convenience), is introduced by a pipe 46 into acontinuous hopper 48 from which valve-regulated amounts of char are fedby a pipe 50 into the open space above the oxidation zone.

The char is maintained in a dense fluidized phase which serves as theoxidation zone. Elemental Fe and FeO substantially free of carbonaceoussolids are introduced directly into the interior of the fluidized-bedfrom a source and a manner to be later described. The elemental Fe andFeO being of greater density than the fluidized char, descend in the bedin countercurrent flow relationship to steam which is introduced by asteam pipe 52 after being compressed by a jet compressor 53. Under thetemperature and pressure conditions maintained in the oxidation zone,the steam reacts preferentially and rapidly with the elemental Fe andFeO as set forth in equations 4 and 5 above, to form hydrogen. At leastsome of the latter reacts with the char in the fluidized bed to formmethane. The methane is discharged together with unused steam through aneffluent gas pipe 54 for suitable treatment to recover a high B.t.u.gas.

The conditions maintained in the oxidation zone of the preferredembodiment are as follows: temperature, 1400 to 1800 F.; pressure, 100to 1500 p.s.i.; and residence time of char, 1 to 200 minutes, with thehigher pressures and longer residence times being preferred for methaneproduction.

The mixture of iron oxides, mostly Fe O, and FeO, along withcarbon-depleted char, is withdrawn from the oxidation zone through apipe 56. This mixture is lifted to the reduction zone through a liftpipe 58 by means of steam from the steam feed pipe 52. ln recycling tothe reduction zone, the solids pass through a cyclone separator 60 whichseparates the steam from the solids. The steam is returned through aconduit 62 to the oxidation zone after being compressed to the desiredpressure, together with the rest of the inlet steam in the compressor53. The solids drop out of the cyclone 60 into the space above themoving bed and thence onto the moving bed in the reduction zone.

The reduction zone, as in the case of the embodiment shown in FIG. 1,consists essentially of a downwardly moving bed of two substantiallyconcurrently flowing streams of solids. The recycled iron oxides aremixed with the hot stream of carbonaceous solids entering the vesselfrom a lift pipe 66 whose function will be more fully described below.The gas produced in the reduction zone is discharged through a pipe 68.The conditions maintained in the reduction zone of the preferredembodiment are as follows: temperature, l500 to 2100 F.; pressure, 100to 1500 p.s.i.; residence time, 1 to 30 minutes; carbon depletion perpass, I to 10 percent of the carbon in the carbonaceous solids; andweight ratio of char to iron oxides, 0.5 to 5 lb./lb.

The mixture of reduced iron oxides, principally Fe and FeO, along withpartially carbon-depleted carbonaceous solids drops by gravity throughan outlet conduit 70 to a separator 72. The latter is adapted to confinethe mixture of solids in a fluidized state, the fluidizing gas beingintroduced by a pipe 74. The fluidizing gas may be essentially inert, orit may contain some steam. If it does contain steam, then some hydrogenmay be generated, in which case the effluent gas from the separator maybe conducted to the Oxidizer. Otherwise, the effluent gas may bedischarged conveniently through conduit 75. Because of the differentdensities of the carbonaceous solids and the iron compounds,fluidization conditions can be selected to permit the iron compounds tosettle out of the bed to be discharged through a conduit 76 into theoxidation zone 42. The fluidized char overflows into a pipe 78 whichleads to the previously mentioned lift pipe 66. Air is introduced intothe foot of the lift pipe through a pipe 80 not only to lift the solidsback to the reductor, but also to burn part of the carbonaceous solidsunder controlled conditions to raise the temperature of the solidssufficiently high to provide the heat required in the reduction zone.Additional air may be introduced into the space above the reduction zonethrough a pipe 82 to effect combustion of the carbon monoxide generatedin the reduction zone, as well as some of the carbonaceous solids fromthe lift pipe 66.

The following example illustrates the operation of the preferredembodiment.

The conditions maintained and results obtained in a material balance runare set forth in the following table 1 wherein the conditions andcompositions of the various gas and solids streams are tabulated. Thegas streams are designated by numerals 1 to 8 inclusive, and the solidsstreams by letters A to H inclusive. The so designated streams are shownin FIG. 3 by the encircled numerals or letters, as the case may be. inaddition, the pressures in pounds per square inch are shown by theencircled 3-digit numbers at several points throughout the I system.

A modification of the preferred embodiment is shown in F IG. 4. Numeralsand 102 designate the Oxidizer and the Reducer respectively. TheOxidizer consists of two superimposed fluidized zones, Zone 1 and Zone11, designated by the numerals 104 and 106 respectively. Zone 1 isintended to serve primarily for the reaction of carbonaceous solids withhydrogen to make methane, while Zone 11 is intended to serve primarilyfor the reaction of steam and Fe or FeO to make SOLl DS STREAMS Number AB C D E F G 11 Lb./hr.

Temperature,

Composition,

wt. percent:

hydrogen. The Reducer 102 consists of three superimposed zones,designated by the numerals 108, 110, and 112 respectively. Zone 108 is amixing chamber wherein incoming Fe O, and FeO and carbonaceous solidsare mixed. Zone 110 is a combustion zone where carbon monoxide and/orthe carbonaceous solids, while falling freely in admixture with the ironoxides, are partially burned to supply heat. Zone 112 is the reductionzone itself, consisting of a downwardly moving bed of the mixture ofiron oxides and carbonaceous solids.

The operation of the process illustrated in FIG. 4 is as fol- 50 lows.Solid lines indicate solids streams and dotted lines, gas

streams. Hydrocarbonaceous solids (identified as carbon") containing avolatile hydrocarbonaceous component and a fixed carbon component arefed continuously through 114 into the Zone I of the Oxidizer 100. Afluidized bed of the hydrocarbonaceous solids is maintained at atemperature between 1400 and 1800 F. and at a pressure between 100 and1500 p.s.i. in order to optimize the reaction between thehydrocarbonaceous solids and hydrogen. The product gas comprisingprincipally methane and hydrogen is withdrawn through a conduit 116,after being freed of solids and condensibles which are shownschematically as discharged through conduit 117. The partially reactedcarbonaceous solids from Zone I are conducted by gravity down through aconduit 118 to the lower Zone 11. In this zone, a fluidized bed; ofcarbonaceous solids is maintained at a temperature between 1400' and1800 F. and at a pressure between 100 and 1500 psi. The gaseous productfrom this zone contains;

principally hydrogen and unreacted steam, with some C0, C0,, and CH,,and is conducted through a conduit 120 to the upper Zone ll to serve asfluidizing reactant in Zone I.

The mixture of iron oxides from Zone 11 is withdrawn therefrom through aconduit 122 to an iron oxide lift pipe 124 wherein the mixture of oxidesis lifted by steam introduced through a conduit 126. The temperature inthe lift pipe is maintained, by suitable regulation of the temperatureof the steam and iron oxides, between l300 and l800 F., therebypromoting the reaction of the steam with FeO in the feed to the liftpipe to form Fe O The latter is separated from the effluent gases by anysuitable means at the top of the lift pipe. The iron oxides comprisingprincipally Fe O and FeO are carried by a conduit 128 to the mixingchamber 108 at the top of the Reducer vessel where they are mixed withchar entering the mixing chamber from conduit 148.

The iron oxides and char which are intimately mixed in the mixingchamber 108 are then allowed to fall freely through the combustion zone110. The latter is suitably supplied with air through a conduit 130, insufficient quantity to partially burn the char and thereby raise thetemperature of the mixture of solids to that required for reduction ofthe iron oxides. Effluent gas and ash are discharged from the combustionzone by any suitable means, schematically shown in the figure as twoconduits 132 and 134 respectively. 7

FeO formed by the reaction of steam and Fe or FeO in the Separator, isconducted to Zone ll via conduit 158 from the Separator. The effluentgas from the Separator, including any hydrogen formed by the reaction ofsteam and Fe or FeO in the Separator, is conducted to Zone ll by aconduit 160, joining up with conduit 154 at the inlet to Zone ll.

The following example illustrates the operation of the modification ofthe preferred embodiment shown in FIG. 4.

The conditions maintained and results obtained in a material balance runare set forth in the following Table II wherein the conditions andcompositions of the various gas and solids streams are tabulated. Thegas streams are designated by numerals l to 14 inclusive, and the solidsstreams by letters A to L inclusive. The so designated streams are shownin FIG. 5 by the encircled corresponding numerals or letters. Inaddition, the temperatures in F. of the several streams are shown by the4-digit numbers in parentheses.

TABLE II.GAS STREAMSPOUND MOLES/HOUR ash content of the char.

Associated with the "Given in Lbs/hr.

The hot mixture of iron oxides and char is dropped onto the top ofdownwardly moving bed 112 wherein the iron oxides are reduced to Fe andFeO, Theonly gases present in the moving bed are those generated in situas schematically illustrated by the dotted arrow 136. The solid productfrom the reduction zone is removed through a conduit 138 to a Separator140. A fluidized bed is maintained in this Separator as described before, and the velocity of the fluidizing gas is so regulated that thereduced iron oxides drop down while the char remains in a fluidizedstate and overflows through a separate discharge conduit 142. The charis recycled to the Reducer through a lift pipe 144 by means of airintroduced through conduit I46. The air also serves, as before, to burnpart of the char for process heat. The hot solids are conducted from thetop of the lift pipe through a conduit 148 to the mixing chamber 108.The effluent gas from the lift pipe 144 is also conducted to the mixingchamber and is shown schematically, in order to show all gas streams aswell as solids streams, as being conducted through a separate conduit150, although it would normally not be handled separately.

The gas stream issuing from the top of the iron oxide lift pipe 124. asstated before, comprises principally hydrogen and unreacted steam. Thisgas stream is carried by conduits 152 and 154 to Zone ll; and, ifdesired, a slip stream may be conducted to the Separator 140 by means ofa conduit 156. Thus, it may serve as the fluidizing gas in theSeparator; but, in that case, in the course of passing in contact withthe reduced iron oxide, will reoxidize at least some of the Fe to FeO,which in turn will react, at least to some extent, with the steam toform hydrogen. The mixture of reduced iron oxides, including any Weclaim:

1. A continuous process for making hydrogen which comprises:

a. passing a stream of particulate iron oxides comprising principallyFe;,0.i and FeO and a stream of particulate carbonaceous solidsconcurrently and downwardly into the top of a reduction zone, subjectingsaid stream of particulate iron oxides to direct reactive contact withsaid stream of particulate carbonaceous solids in a downwardly movingbed in said reductionzone, there being no molecular oxygen-containinggas introduced into the moving bed in the reduction zone,

. maintaining the following conditions in said reduction zone:temperature, l000 to 2600 F.; pressure, atmospheric or superatmospheric;residence time of said solids, 15 seconds to 60 minutes; carbondepletion per pass, 1 to 10 percent of the carbon in said carbonaceoussolids; and a carbon content of said carbonaceous solids which is atleast 20 percent by weight, whereby the iron oxides are reduced to amixture comprising principally F c0 and Fe,

d. partially burning carbon-depleted carbonaceous solids from step boutside the reduction zone to raise the temperature of said carbonaceoussolids sufficiently high to supply adiabatically the heat required insaid reduction zone,

e. returning said partially burned carbonaceous solids from step d tosaid reduction zone,

solids consumed in the process,

reacting reduced iron oxides from step b with steam in an oxidationzone,

maintaining the following conditions in said oxidation zone:temperature, 1000 to 2000 F.; pressure, atmospheric or superatmospheric;and residence time of solids, 0.5 to 200 minutes, whereby hydrogen isformed and a mixture of iron oxides comprising principally F e 0 and FeOis produced, and

. returning said mixture of iron oxides from step g to said reductionzone of step a to repeat the cycle. The process according to claim 1 inwhich the reduction zone is maintained at a temperature between [500 and2100 F. and a pressure between 100 and [500 p.s.i.; and the oxidationzone is maintained at a temperature between 1400 and 1800 F. and apressure between 100 and i500 p.s.i.

3. prises:

A continuous process for making hydrogen which compassing a stream ofparticulate iron oxides comprising principally Fe 0 and FeO and a streamof particulate: carbonaceous solids concurrently and downwardly into;the top of a reduction zone,

. subjecting said stream of particulate iron oxides to direct reactivecontact with said stream of particulate carbonaceous solids in adownwardly moving bed in said reduction zone, there being no molecularoxygen-containing gases introduced into said moving bed in saidreduction zone, maintaining the following conditions in said reductionzone: temperature, [000 to 2600 F.; pressure, atmospheric orsuperatmospheric; residence time of solids, 15 seconds to 60 minutes;carbon depletion of p.s.i.; carbonaceous solids per pass through saidreduction zone, 1 5 to 10 percent of the carbon in said carbonaceoussolids; and a carbon content of said carbonaceous solids which is atleast 20 percent by weight, whereby said iron oxides are reduced to amixture comprising principally FeO and Fe,

withdrawing the mixture of carbon-depleted carbonaceous solids andreduced iron oxides from said reduction zone and transferring saidmixture to a separation zone, passing a gas through said mixture ofcarbon-depleted carbonaceous solids and reduced iron oxides in saidseparation zone at a velocity sufficient to effect separation by virtueof the difference in densities of the reduced iron oxides andcarbonaceous solids; withdrawing carbon-depleted carbonaceous solidsfrom said separation zone and partially burning same outside saidreduction zone to raise the temperature of said carbonaceous solidssufficiently high to supply adiabatically the heat required in saidreduction zone;

g. returning said partially burned carbonaceous solids to said reductionzone,

h. withdrawing iron oxides from said separation zone and reacting samewith steam in an oxidation zone,

4 The process according to claim 3 in which the reduction zone ismaintained at a temperature between l500 and 2l00 F. and a pressurebetween 100 and 1500 p.s.i.; and the oxidation zone is maintained at atemperature between l400 and 1800 F. and a pressure between l00 and i500p.s.i.

5. A continuous process for making hydrogen which comprises:

a. passing a stream of particulate iron oxides comprising principally FeQ, and FeO and a stream of particulate carbonaceous solids concurrentlyand downwardly into the top of a reduction zone, Subjecting said streamof particulate iron oxides to direct reactive contact with said streamof particulate carbonaceous solids in a downwardly moving bed in saidreduction zone, there being no molecular oxygen-containing gasesintroduced into said moving bed in said reduction zone,

c. maintaining the following conditions in said reduction zone:temperature, l000 to 2600 F pressure, atmospheric or superatmospheric;residence time of solids,

15 seconds to minutes; carbon depletion of said carbonaceous solids perpass through said reduction zone, I to 10 percent of the carbon in saidcarbonaceous solids; and a carbon content of said carbonaceous solidswhich is at least 20 percent by weight, whereby said iron oxides arereduced to a mixture comprising principally FeO and Fe,

d. withdrawing the mixture of carbon-depleted carbonaceous solids andreduced iron oxides from said reduction zone and transferring saidmixture to a separation zone,

e. Passing a fluidizing gas through said mixture of carbondepletedcarbonaceous solids and reduced iron oxides in said separation zone atsuch a velocity that a fluidized bed of said carbonaceous solids isestablished and maintained from which said iron oxides and saidcarbonaceous solids may be separately withdrawn,

f. withdrawing carbon-depleted carbonaceous solids from said fluidizedseparation zone and partially burning same outside said reduction zoneto raise the temperature of said carbonaceous solids sufficiently highto supply adiabatically the heat required in said reduction zone;

g. returning said partially burned carbonaceous solids to said reductionzone,

h. withdrawing iron oxides from said separation zone and reacting samewith steam in an oxidation zone,

. maintaining the following conditions in said oxidation zone:temperature, l000 to 2000 F pressure, atmospheric or superatmospheric;and residence time of the solids, 30 seconds to 200 minutes, wherebyhydrogen is formed and a mixture of iron oxides comprising principallymo, and FeO is produced,

j. returning said mixture of iron oxides from said oxidation zone tosaid reduction zone, and

adding carbonaceous solids to replenish the carbonaceous solids consumedin the process.

6. The process according to claim 5 in which the reduction maintainingthe following conditions i d o at on 60 zone is maintainedatatemperature between l500 and 2l00 returning said mixture of ironoxides from said oxidation zone to said reduction zone, and

adding carbonaceous solids to replenish the carbonaceous solids consumedin the process.

F. and a pressure between and 1500 p.s.i.; and the oxidati n zone ismaintained at a temperature between 1400 and [800 F. and a pressurebetween 100 and i500 p.s.i. 7. The process according to claim 5 in whichthe fluidizing 65 gas used in the separation zone is an inert gas.

8. The process according to claim 5 in which the fluidizing gas used inthe separation zone contains steam.

* lt =i l gggg g UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No. 3,619 ,142 Dated November 9 1971 Inventor(s) James L. Johnsonet a]..

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Col. 6, line ll: Under "Temperature, F., l,l65"(#6) (Table I) shouldread -1,656--;

CO1. 7,Table II: CZHQ should read -"c2H5- Col.7, Table II: Headingbetween the two parts of the Table should be inserted to read -SolidsStreams lb. moles/hr.-;

Col. 9, line 34: After "carbon depletion of, change (Claim 3) "p.s.i.;"to read -said--.

Signed and sealed this 24th day of April 1973.

(SEAL) Attest:

ROBERT GOTTSCHALK A ER,JR. EDWARD M PLETC Comm issloner of Patents\ttestimg Officer

2. The process according to claim 1 in which the reduction zone ismaintained at a temperature between 1500* and 2100* F. and a pressurebetween 100 and 1500 p.s.i.; and the oxidation zone is maintained at atemperature between 1400* and 1800* F. and a pressure between 100 and1500 p.s.i.
 3. A continuous process for making hydrogen which comprises:a. passing a stream of particulate iron oxides comprising principallyFe3O4 and FeO and a stream of particulate carbonaceous solidsconcurrently and downwardly into the top of a reduction zone, b.subjecting said stream of particulate iron oxides to direct reactivecontact with said stream of particulate carbonaceous solids in adownwardly moving bed in said reduction zone, there being no molecularoxygen-containing gases introduced into said moving bed in saidreduction zone, c. maintaining the following conditions in saidreduction zone: temperature, 1000* to 2600* F.; pressure, atmospheric orsuperatmospheric; residence time of solids, 15 seconds to 60 minutes;carbon depletion of p.s.i.; carbonaceous solids per pass through saidreduction zone, 1 to 10 percent of the carbon in said carbonaceoussolids; and a carbon content of said carbonaceous solids which is atleast 20 percent by weight, whereby said iron oxides are reduced to amixture comprising principally FeO and Fe, d. withdrawing the mixture ofcarbon-depleted carbonaceous solids and reduced iron oxides from saidreduction zone and transferring said mixture to a separation zone, e.passing a gas through said mixture of carbon-depleted carbonaceoussolids and reduced iron oxides in said separation zone at a velocitysufficient to effect separation by virtue of the difference in densitiesof the reduced iron oxides and carbonaceous solids; f. withdrawingcarbon-depleted carbonaceous solids from said separation zone andpartially burning same outside said reduction zone to raise thetemperature of said carbonaceous solids sufficiently high to supplyadiabatically the heat required in said reduction zone; g. returningsaid partially burned carbonaceous solids to said reduction zone, h.withdrawing iron oxides from said separation zone and reacting same withsteam in an oxidation zone, i. maintaining the following conditions insaid oxidation zone: temperature, 1000 to 2000* F.; pressure,atmospheric or superatmospheric; and residence time of the solids, 30seconds to 200 minutes, whereby hydrogen is formed and a mixture of ironoxides comprising principally Fe3O4 and FeO is produced, j. returningsaid mixture of iron oxides from said oxidation zone to said reductionzone, and k. adding carbonaceous solids to replenish the carbonaceoussolids consumed in the process.
 4. The process according to claim 3 inwhich the reduction zone is maintained at a temperature between 1500*and 2100* F. and a pressure between 100 and 1500 p.s.i.; and theoxidation zone is maintained at a temperature between 1400* and 1800* F.and a pressure between 100 and 1500 p.s.i.
 5. A continuous process formaking hydrogen which comprises: a. passing a stream of particulate ironoxides comprising principally Fe3O4 and FeO and a stream of particulatecarbonaceous solids concurrently and downwardly into the top of areduction zone, b. Subjecting said stream of particulate iron oxides todirect reactiVe contact with said stream of particulate carbonaceoussolids in a downwardly moving bed in said reduction zone, there being nomolecular oxygen-containing gases introduced into said moving bed insaid reduction zone, c. maintaining the following conditions in saidreduction zone: temperature, 1000* to 2600* F.; pressure, atmospheric orsuperatmospheric; residence time of solids, 15 seconds to 60 minutes;carbon depletion of said carbonaceous solids per pass through saidreduction zone, 1 to 10 percent of the carbon in said carbonaceoussolids; and a carbon content of said carbonaceous solids which is atleast 20 percent by weight, whereby said iron oxides are reduced to amixture comprising principally FeO and Fe, d. withdrawing the mixture ofcarbon-depleted carbonaceous solids and reduced iron oxides from saidreduction zone and transferring said mixture to a separation zone, e.Passing a fluidizing gas through said mixture of carbon-depletedcarbonaceous solids and reduced iron oxides in said separation zone atsuch a velocity that a fluidized bed of said carbonaceous solids isestablished and maintained from which said iron oxides and saidcarbonaceous solids may be separately withdrawn, f. withdrawingcarbon-depleted carbonaceous solids from said fluidized separation zoneand partially burning same outside said reduction zone to raise thetemperature of said carbonaceous solids sufficiently high to supplyadiabatically the heat required in said reduction zone; g. returningsaid partially burned carbonaceous solids to said reduction zone, h.withdrawing iron oxides from said separation zone and reacting same withsteam in an oxidation zone, i. maintaining the following conditions insaid oxidation zone: temperature, 1000* to 2000* F.; pressure,atmospheric or superatmospheric; and residence time of the solids, 30seconds to 200 minutes, whereby hydrogen is formed and a mixture of ironoxides comprising principally Fe3O4 and FeO is produced, j. returningsaid mixture of iron oxides from said oxidation zone to said reductionzone, and k. adding carbonaceous solids to replenish the carbonaceoussolids consumed in the process.
 6. The process according to claim 5 inwhich the reduction zone is maintained at a temperature between 1500*and 2100* F. and a pressure between 100 and 1500 p.s.i.; and theoxidation zone is maintained at a temperature between 1400* and 1800* F.and a pressure between 100 and 1500 p.s.i.
 7. The process according toclaim 5 in which the fluidizing gas used in the separation zone is aninert gas.
 8. The process according to claim 5 in which the fluidizinggas used in the separation zone contains steam.